Liquid crystal panels utilizing polarizers are well known as optical modulators. Such a liquid crystal panel controls the transmittance of light incident on the liquid crystal panel by converting natural light before being incident on a liquid crystal layer into polarized light using a polarizer and then causing the polarized light passing through the liquid crystal layer to enter the same polarizer (in the case of a reflective mode) or another polarizer (in the case of a transmissive mode). A liquid crystal layer can be utilized in polarization control because the alignment of liquid crystal molecules in the liquid crystal layer varies according to the voltage applied. In such a liquid crystal panel, however, half or more of the light used for display is absorbed by the polarizer, which unfortunately puts a limit on increase in light use efficiency.
In order to deal with this problem, optical modulators requiring no polarizer, such as those disclosed in Patent Literatures 1 to 8, have been developed. Patent Literature 1 discloses an optical device wherein a system containing electro-optically sensitive flakes suspended in a fluid host is encapsulated in a polymeric binder solution. Patent Literature 2 discloses a display medium containing scaly magnetic powder dispersed in a liquid in microcapsules surrounded by a binder. Patent Literature 3 discloses an electrochemical display element comprising, between two electrode plates, an ionic conductor containing fine particles of a specific organic polymer and an electrolyte held in the polymer fine particles. Patent Literatures 4 and 5 each disclose an optical modulation panel comprising an optical modulation layer that contains a shape-isotropic member. Patent Literatures 6 and 7 each disclose an optical device including a suspension layer containing polymer flakes. Patent Literature 8 discloses a transflective display including a suspension layer that contains reflective particles.
Meanwhile, surface modification of particles has been studied in the field of paints, for example. Examples of known techniques include those disclosed in Patent Literatures 9 to 16.